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Raising Halibut

 


Raising Halibut
Seven years of UMaine aquaculture research is paying off

About the Photo: Collecting eggs from an adult female halibut are CCAR research assistant Marcela Hincapie and operations manager Nick Brown. Every three days during breeding season, a single adult female halibut can supply several liters of the fragile eggs, which are carefully blended with milt collected from the males. In a darkened room humming with the sound of pumps and filters, long columnar tanks act as swirling incubators for the fertilized eggs.
 

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Wanda swims lazily in an 8,500-gallon black plastic tank until she senses the approach of visitors. Then she breaks the surface of the cold, clear water in a frenzied greeting exacerbated by the natural orientation of her head, permanently cocked to one side in the trademark twist of her species.

Far removed from her deepwater ocean haunts, she is one of more than 100 adult Atlantic halibut being raised as brood stock at the University of Maine Center for Cooperative Aquaculture Research (CCAR) in Franklin, Maine. Wanda and her companions supply the eggs and milt that seed the production lines of CCAR's halibut aquaculture program, turning a diet of carefully formulated krill, squid, crab and fish sausages into the next generation of Hippoglossus hippoglossus.

Wanda weighs in at a hefty 120 pounds, the first big hint that there are peculiarities of the halibut's life cycle that make the rules for raising such bottom-hugging beauties unlike those for raising goldfish. In truth, the halibut's journey from egg to plate is as complicated as its twisted visage is bizarre. A tremendous research investment is required to achieve success in the feeding, breeding and rearing of each tasty filet. UMaine's halibut program represents more than seven years of research into the unusual lives of the flatfish and benefits to Maine's aquaculture industry that have only begun to be realized.

"There has been a lot to discover with halibut," says Nick Brown, CCAR operations manager. "Marine species are notoriously difficult to raise in terms of nutrition and other factors, and since halibut spawn in deep water, we know even less about them."

Brown and his UMaine research colleagues have applied their considerable expertise to unraveling the secrets of halibut growth and development, pairing their discoveries with an adaptive, innovative approach to developing successful systems for large-scale production. Utilizing the facility's resident adult population, wild caught in Maine waters in 200001, the scientists began harvesting eggs and milt from the huge fish and identifying optimal conditions for hatching and rearing halibut larvae.


Every three days during breeding season, a single adult female can supply several liters of the fragile eggs, which are carefully blended with milt collected from the males. In a darkened room humming with the sound of pumps and filters, long columnar tanks act as swirling incubators for the fertilized eggs. Once hatched, the tiny, translucent fry are at the most delicate stage in their development.

For nearly 10 weeks, they swim in much the same way as other fish. After absorbing their yolk sac, they seek out minuscule prey to build energy for their surprising metamorphosis. With the proper food and environmental conditions, the bodies of the tiny fish transform from a typical salmon-like design to the horizontally flattened form of the adult. Their bodies twist and flatten, their eyes migrate to one side and they slowly descend through the water column to their new home on the ocean floor.

The slightest environmental disturbance or nutritional deficiency can throw the halibut larvae's delicate systems off balance, causing an irregular or incomplete metamorphosis that leads to deformities. Brown and his team have successfully identified the environmental and nutritional requirements for larval growth, and can now rear tens of thousands of larvae in the Franklin facility for research and commercial aquaculture.

Brown also has teamed up with UMaine aquaculture nutrition expert Linda Kling. Their research, funded by a grant from the USDA Northeastern Regional Aquaculture Center, includes the longest-running halibut brood stock nutrition study ever conducted. Testing two specially formulated diets against a control diet of raw herring and squid, Brown and Kling have made significant strides toward understanding the complex nutritional needs of adult halibut, comparing differences in growth rates, egg production rates and larval success based on feeding regimes.

Addressing the challenges of halibut aquaculture in a comprehensive way has allowed the center to become a true partner in the development of the state's aquaculture industry. By examining everything from breeding to feeding, UMaine has been able to offer its industry partners a head start in the growing halibut aquaculture market.

"We have been working with UMaine since 2002 in a business incubator-type relationship, and we are very enthusiastic about what the future holds," says Alan Spear, president of Maine Halibut Farms LLC of Orono. "Raising halibut commercially is a process that requires a long lead time and considerable capital investment. Our relationship with UMaine has given us the chance to prove our model works and carve a niche for ourselves in the industry."

The successful relationship between CCAR and its industry partners was highlighted by the sale of a bumper crop of more than 25,000 healthy juvenile halibut to Maine Halibut Farms in 2006. The fish represent the first large-scale population of commercially grown halibut in the country and are an important step toward establishing a halibut aquaculture industry in Maine.


Research into nutrition and rearing methods has been critical to the program's success, but UMaine's role in developing the fledgling halibut aquaculture industry isn't limited to researching the fish's unique biology. CCAR's innovative facilities and management methods are helping ensure that raising halibut will be a commercially viable enterprise in the state. From temperature-controlled incubation rooms to advanced recirculation technologies, CCAR's facilities and techniques have revealed new ways to reduce costs, increase growth and prevent disease.

One of CCAR's most important advances has been in the recirculation systems being used to house the adult brood stock, and in incubation and larval rearing. To maintain healthy conditions for growth and breeding, the huge tanks require a complete water change every hour, amounting to almost a million gallons per day cycling through the brood stock facility.

Seawater inputs this large not only increase energy and maintenance costs for pumps and associated equipment, but also make temperature, salinity and other water conditions nearly impossible to control. CCAR's recirculation system not only cleans the water and allows technicians greater control, it also limits fresh seawater inputs to just 4,000 gallons per day.

"With this system, we are able to filter the water and sterilize it using ultraviolet light, as well as control salinity and temperature in the tanks," says Brown. "We are always trying new things to boost the efficiency of the system and reduce costs."

The filter takes advantage of the natural ability of bacteria to break down fish wastes such as ammonia into harmless nitrates. As pumps churn billions of bubbles through a mixture of tank water and dime-size plastic nuggets, bacteria growing on the surface of the plastic work their magic, creating a giant biofilter for processing the considerable waste produced by dozens of adult halibut.

With 25,000 young halibut at CCAR, a major facility expansion is under way. Giant concrete tanks and new technologies have been installed to expand the program's ability to grow halibut to a market size of 510 pounds, and market tests are being conducted to determine if smaller, plate-sized halibut would appeal to consumers. Capable of supporting 500,000 fish, the new expansion will allow CCAR and its industry partners to complete the progression from proof-of-concept experimentation to demonstrable, large-scale production.

The successful expansion is clearly a good sign for Maine's aquaculture industry.

"Restrictions on wild-caught halibut have opened up more markets in Boston and New York for farmed halibut, and most of what's being raised currently is coming from Norway, Scotland and Canada," says Spear.

"This new phase of the project will bring us up to a production level of 20 tons per year," he says. "When we take the next step to 200 tons per year, we'll have a real, viable business under way."

by David Munson
January-February, 2008

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